Exam 34: Emission Control Diagnosis and Service

Excessively high HC emissions may be caused by ______.

Technician A says when CO goes up, O₂ goes down.Technician B says at the stoichiometric point [14.7:1], HC and CO will be at their lowest levels and CO₂ will be at its highest. Who is correct?

A water manometer for testing crankcase pressure/vacuum can be made from a 2 foot length of _____________________.

Identify the two causes of lower than normal CO₂ emissions.

Excessive carbon monoxide [CO] forms when there is not enough O₂ to combine with the carbon during combustion.

A catalytic converter can be tested with a rubber mallet.

Crankcase pressure forcing crankcase gases through the clean air hose and into the air cleaner is being discussed. Technician A says the cause may be an excessive amount of blowby. Technician B says the cause may be a restricted PCV valve. Who is correct?

Technician A says if the EGR valve does not open, the engine may emit excessive amounts of HC. Technician B says if the EGR valve does not open, the engine may detonate on acceleration. Who is correct?

Excessive oil consumption can be caused by a plugged PCV hose.

Higher than normal ____________________ emissions may be caused by an overheated engine.

What happens if a PCV valve is stuck in the open position?

All EGR valves can be tested with a vacuum gauge while the engine is idling.

If the PCV valve is stuck in the open position, a lean air/fuel ratio may cause a rough idle or engine stalling.

Technician A says a loose oil filler cap or a dip stick that is not fully seated in the dipstick tube can change the LTFT on a MAF system. Technician B says the PCV system will draw unfiltered air through these leaks which could result in premature wear of engine parts. Who is correct?

During an I/M 240 test, the vehicle's exhaust is collected by a CVS system.

A stuck open EGR valve could cause _____.

Technician A says retrieving DTCs from the control system is the best beginning for diagnosing emission problems. Technician B says because a single emissions system component failure can set multiple DTCs, codes should be used only to confirm the effectiveness of the repairs. Who is correct?

High ___________________ emissions are associated with an inoperative EGR valve.

What is an OBD-II monitor?

Technician A says the AIRB valve directs secondary air either to the intake manifold or to the catalytic converter. Technician B says with the engine at normal operating temperature, the AIR system sometimes goes back into upstream mode with the engine idling. Who is correct?